This invention relates to a method and apparatus for producing reducing gas, and more particularly to a method and apparatus for producing high calorie reducing gas by using a slag-tap type gas manufacturing furnace and a high calorie substance, for example, heavy oil asphalt and plastic discards.
A number of types of the slag-tap type gas manufacturing furnaces have been described and used commercially in which a solid carbonaceous substance, such as coal and coke, is charged in a shaft furnace and gasified by a mixture of stem and oxygen or oxygen-rich air blasted into the furnace through tuyeres at the hearth of the furnace. The resulting reducing gas is discharged from the furnace top and a molten slag of the ash components is discharged from the furance crucible.
In such a furnace, the solid carbonaceous substance is preheated by the steam and oxygen blown into the furance through the tuyeres, and caused to react with the steam and oxygen at the inlet ends of the tuyeres according to the following equation ##STR1## While rising upwardly, the resulting gas reacts with red heat coal or coke according to the following equation 2, thus forming hydrogen and carbon monoxide: EQU H.sub.2 0 + C0.sub.2 + C0 (2.)
The ash components consisting essentially of Si0.sub.2, A1.sub.2 0.sub.3, etc. of the coal or coke react with a blast furnace slag or lime stone which is charged into the furnace through the top thereof together with the carbonaceous substance for forming a slag having relatively low melting points. The slag is collected in the crucible of the furnace in a molten state and is discharged to the outside through a tap hole. The molten slag discharged through the tap hole is collected in a water bath to solidify. The resulting gas mixture is used as fuel and the composition thereof generally comprises 50 to 80% CO and about 20% of hydrogen and its heat value is low, of the order of about 3000 Kcal/Nm.sup.3. It is reported that gas consisting of 72.4% of C0 and 22.6% of H.sub.2 has a heat value of 2915 Kcal/NM.sup.3. For this reason, in order to use such a gas as fuel gas, it is common to increase its heat quantity by mixing it with high calorie gas such as LPG and butane. The coal utilized as the raw material for operating the slag-tap gas manufacturing furnace generally contains substances which evaporate at low temperatures and the vapor of such substances is discharged from the furnace top together with the gas formed. When cooled, such vapor condenses into an oily substance containing tar, hydrocarbons, free carbons, etc., thus causing various troubles for efficient operation of the furnace. To recover such oily substances as by-products for utilizing them as the raw material for petroleum industry, a large expense is required.
Accordingly, such expensive recovering operations contribute only a little to modern highly developed petroleum industry, and the development of a method and apparatus capable of producing reducing gas of high calorific or heat value without the difficulties described above has long been desired.